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Re: [Qemu-devel] [PATCH v4] hw/block: better reporting on pflash backing
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-devel] [PATCH v4] hw/block: better reporting on pflash backing file mismatch |
Date: |
Fri, 22 Feb 2019 19:44:25 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
Two trivial comments:
On 02/22/19 16:44, Alex Bennée wrote:
> It looks like there was going to be code to check we had some sort of
> alignment so lets replace it with an actual check. This is a bit more
> useful than the enigmatic "failed to read the initial flash content"
> when we attempt to read the number of bytes the device should have.
>
> This is a potential confusing stumbling block when you move from using
> -bios to using -drive if=pflash,file=blob,format=raw,readonly for
> loading your firmware code. To mitigate that we automatically pad in
> the read-only case and warn the user when we have performed magic to
> enable things to Just Work (tm).
>
> Signed-off-by: Alex Bennée <address@hidden>
>
> ---
> v3
> - tweak commit title/commentary
> - use total_len instead of device_len for checks
> - if the device is read-only do the padding for them
> - accept baking_len > total_len (how to warn_report with NULL *errp?)
> v4
> - error check blk_getlength
> - optimise memset and use NOR erase pattern
> - restore singular device (overly confusing)
> - add warn_report for when we do magic
> ---
> hw/block/pflash_cfi01.c | 40 +++++++++++++++++++++++++++++++++-------
> 1 file changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
> index 00c2efd0d7..c69ecc20a0 100644
> --- a/hw/block/pflash_cfi01.c
> +++ b/hw/block/pflash_cfi01.c
> @@ -45,6 +45,7 @@
> #include "qemu/bitops.h"
> #include "qemu/host-utils.h"
> #include "qemu/log.h"
> +#include "qemu/error-report.h"
> #include "hw/sysbus.h"
> #include "sysemu/sysemu.h"
> #include "trace.h"
> @@ -714,13 +715,6 @@ static void pflash_cfi01_realize(DeviceState *dev, Error
> **errp)
> }
> device_len = sector_len_per_device * blocks_per_device;
>
> - /* XXX: to be fixed */
> -#if 0
> - if (total_len != (8 * 1024 * 1024) && total_len != (16 * 1024 * 1024) &&
> - total_len != (32 * 1024 * 1024) && total_len != (64 * 1024 * 1024))
> - return NULL;
> -#endif
> -
> memory_region_init_rom_device(
> &pfl->mem, OBJECT(dev),
> &pflash_cfi01_ops,
> @@ -747,6 +741,38 @@ static void pflash_cfi01_realize(DeviceState *dev, Error
> **errp)
> }
>
> if (pfl->blk) {
> + /*
> + * Validate the backing store is the right size for pflash
> + * devices. It should be padded to a multiple of the flash
> + * block size. If the device is read-only we can elide the
> + * check and just null pad the region first. If the user
(1) We no longer null-pad, but one-pad (bit-wise). I don't think it's
too confusing though.
> + * supplies a larger file we ignore the tail.
> + */
> + int64_t backing_len = blk_getlength(pfl->blk);
> + if (backing_len < 0) {
> + error_setg(errp, "unable to check size of backing file");
> + return;
> + }
> +
> + if (backing_len < total_len) {
> + if (pfl->ro) {
> + size_t pad_bytes = total_len - backing_len;
> + /* pad with NOR erase pattern */
> + memset((uint8_t*)pfl->storage + backing_len, 0xff,
> pad_bytes);
> + warn_report("device needs %" PRIu64
> + " bytes, padded with %zd 0xff bytes",
(2) I think %zu would be more appropriate for size_t, but it's not a
showstopper.
> + total_len, pad_bytes);
> + total_len = backing_len;
> + } else {
> + error_setg(errp, "device needs %" PRIu64 " bytes, "
> + "backing file provides only %" PRIu64 " bytes",
> + total_len, backing_len);
> + return;
> + }
> + } else if (backing_len > total_len) {
> + warn_report("device needs %" PRIu64 " bytes, rest ignored",
> total_len);
> + }
> +
> /* read the initial flash content */
> ret = blk_pread(pfl->blk, 0, pfl->storage, total_len);
>
>
No need to repost just because of these.
Reviewed-by: Laszlo Ersek <address@hidden>
Thanks!
Laszlo